Overeating and excessive weight gain occur when adult rats of either sex are offered a complete diet and a palatable carbohydrate solution. These effects are observed with diets that range in protein content from 10-40% and with glucose, sucrose and maltose solutions. Overeating is eliminated in male rats housed in an activity wheel or with a sexually receptive female. Overeating is also eliminated if access to either dietary component (complete diet or carbohydrate solution) is constrained experimentally. These data appear to have many parallels to the conditions associated with adult-onset obesity in man. The objective of the proposed research is to study the behavioral and physiological correlates of obesity in these animals. Body composition and pancreatic morphology will be examined. Meal patterns, defense of body weight and taste responsivity will also be studied in these overweight animals. A second series of experiments will study dietary selection patterns when graded amounts of carbohydrate solutions or a complete diet are delivered intragastrically in an effort to isolate the factors that control overeating.